Fix uses of /deep/ in trace viewer.

tracing/tracing/ui/extras/chrome/cc/layer_picker.css

-/* Copyright (c) 2013 The Chromium Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-* /deep/ tr-ui-e-chrome-cc-layer-picker {
-  flex-direction: column;
-  display: flex;
-}
-
-* /deep/ tr-ui-e-chrome-cc-layer-picker > top-controls {
-  flex: 0 0 auto;
-  background-image: -webkit-gradient(linear,
-                                     0 0, 100% 0,
-                                     from(#E5E5E5),
-                                     to(#D1D1D1));
-  border-bottom: 1px solid #8e8e8e;
-  border-top: 1px solid white;
-  display: inline;
-  font-size: 14px;
-  padding-left: 2px;
-}
-
-* /deep/ tr-ui-e-chrome-cc-layer-picker > top-controls input[type='checkbox'] {
-    vertical-align: -2px;
-}
-
-* /deep/ tr-ui-e-chrome-cc-layer-picker > .x-list-view {
-  flex: 1 1 auto;
-  font-family: monospace;
-  overflow: auto;
-}
-
-* /deep/ tr-ui-e-chrome-cc-layer-picker > tr-ui-a-generic-object-view {
-  flex: 0 0 auto;
-  height: 200px;
-  overflow: auto;
-}
-
-* /deep/ tr-ui-e-chrome-cc-layer-picker > tr-ui-a-generic-object-view * {
-  -webkit-user-select: text !important;
-  cursor: text;
-}